Independent two-step thresholding of binary images in inter-annual land cover change/no-change identification

Binary images from one or more spectral bands have been used in many studies for land-cover change/no-change identification in diverse climatic conditions. Determination of appropriate threshold levels for change/no-change identification is a critical factor that influences change detection result accuracy. The most used method to determine the threshold values is based on the standard deviation (SD) from the mean, assuming the amount of change (due to increase or decrease in brightness values) to be symmetrically distributed on a standard normal curve, which is not always true. Considering the asymmetrical nature of distribution histogram for the two sides, this study proposes a relatively simple and easy ‘Independent Two-Step’ thresholding approach for optimal threshold value determination for spectrally increased and decreased part using Normalized Difference Vegetation Index (NDVI) difference image. Six NDVI differencing images from 2007 to 2009 of different seasons were tested for inter-annual or seasonal land cover change/no-change identification. The relative performances of the proposed and two other methods towards the sensitivity of distributions were tested and an improvement of ∼3% in overall accuracy and of ∼0.04 in Kappa was attained with the Proposed Method. This study demonstrated the importance of consideration of normality of data distributions in land-cover change/no-change analysis.     

基于NOAA/AVHRR数据的北极反照率反演及其变化研究

极地海冰反照率直接影响极区的热收支,反照率的变化对地气系统热量收支平衡及气候变化等的研究具有重要意义。本文采用由美国国家海洋与大气管理局NOAA (National Oceanic and Atmospheric Administration)发射的NOAA卫星携带的先进的甚高分辨率辐射仪AVHRR (Advanced Very High Resolution Radiometer) Level-1B (L1B) 数据,经宽带反射率转换、各向异性校正、大气订正、云检测等处理,得到4 km宽带晴空地表反照率产品。将AVHRR反照率与北冰洋地表热收支SHEBA (Surface Heat Budget of the Arctic Ocean)实验数据进行印证,印证结果显示在冰雪冻结期二者平均偏差为-0.07,标准偏差为0.05。本文处理了2008年—2010年的AVHRR数据,结合第4次北极科学考察现场观测数据研究了北极冰面月平均反照率的变化,从降雪和冰脊两个方面分析了反照率的变化,结果显示反照率在冰雪融化过程中变化约为0.3,变化较大且较为迅速,表面粗糙的多年冰海域和较为平滑的一年冰海域的反照率在雪融化时期变化约为0.2且变化相对缓慢。研究结果表明,由冰雪融化引起的反照率变化较为快速且幅度较大,是引起北极反照率变化的主导因素。     

基于不同空间信息源的地物光谱反射率模拟图像分析

本文利用ERDAS Imaging软件中的Modeler模块,开发了地物光谱反射率图像的模拟技术。以野外实测地物光谱反射率数据为依据,用土地利用类型图和高分辨率遥感影像图作为地物空间分布的信息源,以陆地资源卫星TM1-4波段为例,模拟了4个波段的地物光谱反射率图像,合成了真彩色和标准假彩色图像。对基于不同空间信息源的地物光谱反射率模拟图像进行了对比分析,指出了进一步研究的方向。     

异源高分辨率光学卫星遥感影像联合定位

本文提出一种基于RFM和投影射线法的异源高分辨率光学卫星遥感影像定位算法:首先利用高分辨率遥感影像RFM正解模型迭代计算其反解模型;接着通过RFM正反解模型构建投影射线,最后采用迭代求取射线交点的方法确定地面三维实际坐标。实验对比结果表明,联合具有一定重叠度的异源高分辨率光学卫星遥感影像进行立体定位具有较强的可行性,并可达到一定的精度。     

VLL影像匹配的线路地形断面测绘方法

针对使用现有全数字摄影测量手段从航空影像中提取线路地形断面,存在高程精度低、劳动强度高以及自动化程度低等缺点,本文在已有数字高程模型(DEM)等数据基础上,采用铅垂线轨迹法(VLL)结合最小二乘匹配以及概率松弛法进行线路地形断面测绘。实验证明,采用本文方法得到的断面精度要优于全数字摄影测量手段所得到的断面,能够满足实际工程的需求。     

Automatic searching of control point in NOAA AVHRR image

This paper discusses the approaches for automatical searching of control points in the NOAA AVHRR image on the basis of data rearrangement in the form of latitude and longitude grid. The vegetation index transformation and multi-level matching strategies have been proven effective and successful as the experiments show while the control point database is established.     

Using Maximum Likelihood (ML) and Maximum A Prior Probability (MAP) in Iterative Self‐Organizing Data (ISODATA)

Abstract

With the availability of high‐resolution satellite imagery featuring as high as 1 meter resolution in the panchromatic mode and 3‐meter resolution in the multispectral mode, there is an interest by many new commercial and public service applications such as cellular telephones coverage area design, urban/land cover planning, and real estate marketing to extract features from images automatically. To that end, the demand for unsupervised classification techniques is growing. In this paper, the Maximum Likelihood (ML) and Maximum A prior Probability (MAP) algorithms are used as decision rules to find boundaries of classes computed by the Iterative Self‐Organizing Data (ISOADATA) algorithm. Different satellite images with different resolutions were used to experiment with these algorithms. The results of comparing and analyzing the algorithms revealed that MAP‐ISODATA performed better than ML‐ISODATA even when the same initial matrix was used. It was shown that there was no significant difference between ML‐ISODATA and MAP‐ISODATA in terms of accuracy. It was also realized that better results could be obtained if homogenous initialization strategies were used.     

Estimation of impervious surfaces of Beijing,China, with spectral normalized images using linear spectral mixture analysis and artificial neural network

The objective of this article is to evaluate the effectiveness of various algorithms for estimating impervious surfaces. Linear spectral mixture analysis (LSMA) and multi-layer perceptron (MLP) network using original and spectral normalized images were applied to two ASTER images acquired on 31 August and 9 April 2004, respectively. Accuracy assessment was performed with a Quickbird image. Root-mean-square errors (RMSEs) were calculated and compared. Results indicated that LSMA with original images provided the poorest results. RMSE was 14.8% for the August image and 22.4% for the April image. Results from LSMA with normalized images improved significantly with RMSE of 12.6% for the August image and 18.9% for the April image. The MLP modelling with original images generated slightly better results with RMSE of 12.2% and 18.4% for each image. The MLP modelling of normalized images provided the best estimation, yielding a RMSE of 12.1% for the August image and 18.2% for the April image.     

滦县县城周边断裂的初步研究

通过卫星影像资料和地质资料,结合浅层地震勘探结果,对滦县县城附近的响堂断裂、坨子头断裂以及唐山断裂进行初步研究,确定3条断裂的活动性质及产状.研究表明滦县县城附近第四系埋深在70～120 m范围内,3条目标断裂都错断了第四系底界,断层上断点位于第四系地层中.     

Application of Principal Component Analysis and Spectral Angle Mapper in the Mapping of Hydrothermal Alteration in the Jebal–Barez Area,Southeastern Iran

The southeastern part of the central Iranian Cenozoic magmatic belt contains many areas with copper mineralization. In an analysis of this region, we used the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper plus (ETM⁺) images to map the distribution of hydrothermally altered rocks, based on their mineral assemblages. The spectral measurements, based on the field samples and satellite‐image‐derived spectra, show dominantly Al–OH (sericite and clays) and Fe–O absorption features in the visible–near infrared to shortwave infrared regions of the spectrum. Silica–bearing rocks, as well as silicic alteration, show an intense Si–O vibrational feature in the thermal infrared wavelength region. We analyzed ASTER/ETM⁺ images, performed a directed principal component analysis, and used spectral angle mapper to map areas of hydrothermal alteration and iron oxide/hydroxide minerals. The individual principal component images compiled by directed principal component analysis reveal the distribution of individual alteration minerals such as sericite, kaolinite, chlorite, epidote, and quartz. The best results, in terms of mapping the distribution of alteration, were obtained using the spectral angle mapper method. The altered areas were then sampled and the samples subjected to X–ray diffraction analysis, spectral analysis, and thin sections were observed under a microscope. Field observations reveal that more than 98% of the known copper mineralization occurs within the interpreted alteration areas. The present results indicate the great potential of ASTER and ETM⁺ data for mapping the distribution of alteration and exploring for copper mineralization in areas with a similar climate and geological setting to those of the present study.